Mechanisms of Islet Beta Cell Dysfunction in Diabetes

糖尿病胰岛β细胞功能障碍的机制

• 批准号: 8394622
• 负责人: Anjaneyulu Kowluru
• 金额: --
• 依托单位: JOHN D DINGELL VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8394622
• 关键词: Age; American; Amputation; Animals; Apoptosis; Apoptotic; BCL2 gene; Beta Cell; Biochemical; Biological; Caspase; Cell Survival; Cells; Ceramides; Chronic; Complex; Data; Defect; Development; Diabetes Mellitus; Event; Fatty Acids; Functional disorder; GTP-Binding Proteins; General Population; Generations; Glucose; Goals; Guanine Nucleotide Dissociation Inhibitors; Guanine Nucleotide Exchange Factors; Health Benefit; Healthcare; Heart Diseases; Holoenzymes; Hydrolysis; Hypertension; Impairment; In Vitro; Islet Cell; Lead; Lipids; Mediating; Mediator of activation protein; Metabolic; Mission; Mitochondria; Modality; Modeling; Molecular; NADPH Oxidase; Non-Insulin-Dependent Diabetes Mellitus; Obesity; Okadaic Acid; Oxidative Stress; Pathway interactions; Patient Care; Population; Prevention; Process; Protein Dephosphorylation; Protein Isoforms; Protein phosphatase; Rattus; Reactive Oxygen Species; Regulation; Reporting; Research; Rodent Model; Role; Signal Transduction; Sphingolipids; Sphingomyelinase; Sphingomyelins; Sphingosine; Testing; Therapeutic; Veterans; base; ceramide-activated protein phosphatase; diabetic; genetic regulatory protein; in vivo Model; inhibitor/antagonist; insight; insulin secretion; islet; member; mitochondrial dysfunction; novel; prevent; research study; response; sphingosine 1-phosphate

Project Summary The sphingolipid ceramide [CER] has been shown to be an important mediator of signal transduction processes leading to a variety of cellular responses, including apoptosis. Despite the compelling experimental evidence to suggest that CER-dependent signaling mechanisms might underlie -cell dysfunction in in vitro and in vivo models of impaired insulin secretion, very little is known with regard to the precise modes of action of CER in the signaling events leading to metabolic dysregulation of the islet -cell. Our preliminary findings suggest that long-term exposure of INS 832/13 cells and primary rat islets to elevated glucose and lipids promote CER-dependent activation of an okadaic acid-sensitive protein phosphatase [CAPP] and the phagocytic NADPH-oxidase [NOX] leading to mitochondrial dysregulation. We also present preliminary evidence to indicate that these two pathways are accelerated in islets from the Zucker Diabetic Fatty [ZDF] rat, a widely accepted model for type 2 diabetes. Based on these data we hypothesize that an accumulation of intracellular CER, induced following chronic exposure of isolated -cells to glucose and lipids, causes mitochondrial dysfunction leading to cell demise. The three Specific Aims of the proposed studies are: [I] to demonstrate that glucolipotoxic conditions promote CER-mediated activation of the mitochondrial isoform of CAPP leading to dephosphorylation and inactivation of Bcl-2 culminating in the mitochondrial dysfunction of the islet -cell; [II] to demonstrate that glucolipotoxic conditions promote CER-mediated holoenzyme assembly and functional activation of NOX to result in the generation of ROS and the associated onset of mitochondrial dysfunction of the islet -cell; and [III] to precisely define the progression, and prevention of mitochondrial defects and metabolic dysfunction [identified under Aims I and II] by CER synthesis inhibitors in the ZDF rat islet. We will employ a number of biochemical, molecular biological, cell biological and immunological approaches to validate our hypothesis and accomplish our goals in INS 832/13 cells, primary rat islets and whole animals. It is hoped that data derived from the proposed studies will provide fresh insights into the regulatory roles of specific CER-sensitive signaling steps in the onset of mitochondrial dysfunction leading to the demise of the islet -cell under the duress of glucolipotoxic conditions. Our long-term goal is to develop specific therapeutic modalities to prevent the establishment of these cell defects and the onset of diabetes. Our proposed studies have direct relevance to the VA research and patient care missions. Available data clearly suggest that veterans are more likely than the general population to have diabetes, one of the major complications associated with obesity. According to the American Diabetes Association, greater than 7% of the U.S. population has diabetes, and the rate increases with age. Among veterans receiving VA health care, who are on average older than the general population, the rate is greater than 20%. According to the VA, 70% of the 7.5 million veterans who receive health benefits through the department are obese, and one in five has diabetes, which can lead to heart disease, high blood pressure and amputations. We envision that data derived from the proposed studies will provide fresh insights into regulatory roles of specific CER-sensitive signaling steps in the onset of mitochondrial dysfunction leading to the demise of the -cell under the duress of glucolipotoxic conditions. The data accrued from our studies might form the basis for the development of specific therapeutic modalities to prevent the establishment of these -cell defects and the onset of diabetes.

项目摘要 鞘磷脂神经酰胺[CER]已被证明是信号转导的重要媒介 导致多种细胞反应的过程，包括细胞凋亡。尽管这个令人信服的实验 有证据表明CER依赖的信号机制可能是体外细胞功能障碍的基础 以及体内胰岛素分泌受损的模型，关于确切的作用模式还知之甚少 CER在导致胰岛细胞代谢失调的信号事件中的作用。我们的初步调查结果 提示INS 832/13细胞和原代大鼠胰岛长期暴露于高糖和高脂 促进依赖CER的冈田酸敏感蛋白磷酸酶[CAPP]的激活和 吞噬细胞NADPH-氧化酶[NOX]导致线粒体失调。我们还提供了初步的 证据表明，这两条途径在Zucker糖尿病肥胖[ZDF]大鼠的胰岛中加速， 一种被广泛接受的2型糖尿病模型。 基于这些数据，我们假设在慢性疾病后，细胞内CER的积聚 分离的细胞暴露在葡萄糖和脂类中，导致线粒体功能障碍，导致细胞死亡。这个 拟议研究的三个具体目标是：[i]证明糖毒性条件促进 CER介导的CAPP线粒体亚型激活导致去磷酸化和失活 最终导致胰岛细胞线粒体功能障碍；[II]以证明糖脂毒性 促进CER介导的全酶组装和NOX功能激活的条件导致 ROS的产生和胰岛细胞线粒体功能障碍的相关发病；以及[III] 准确定义线粒体缺陷和代谢功能障碍的进展和预防[已确定 在目标I和II的作用下，在ZDF大鼠胰岛中使用CER合成抑制剂。我们将雇佣一些生化的， 分子生物学、细胞生物学和免疫学方法来验证我们的假设并实现 我们的目标是在INS 832/13细胞、原代大鼠胰岛和整个动物中进行研究。希望从数据中得出的 拟议的研究将为特定CER敏感信号步骤的调控作用提供新的见解 线粒体功能障碍的开始导致胰岛细胞在压力下死亡 糖脂中毒的情况。我们的长期目标是开发特定的治疗方法来预防 这些细胞缺陷的建立和糖尿病的发病。 我们建议的研究与退伍军人管理局的研究和患者护理任务直接相关。可用数据 清楚地表明，退伍军人比普通人群更有可能患有糖尿病，糖尿病是主要的 与肥胖相关的并发症。根据美国糖尿病协会的数据，超过7%的人 美国人患有糖尿病，而且随着年龄的增长，糖尿病的发病率会增加。在接受退伍军人医疗保健的退伍军人中， 他们的平均年龄比一般人口大，这一比例超过20%。根据退伍军人事务部的数据，70% 在通过卫生部获得医疗福利的750万退伍军人中，有五分之一的人患有肥胖症。 糖尿病，可导致心脏病、高血压和截肢。我们预想到数据是从 将为特定CER敏感信号的调节作用提供新的见解 线粒体功能障碍的始发步骤，导致细胞死亡。 糖脂中毒的情况。从我们的研究中积累的数据可能构成发展的基础 预防这些细胞缺陷和糖尿病发病的具体治疗方法。